Tire and method of making

ABSTRACT

A tire (10) produced via a molding or casting process in a manner such that each of its bead areas (16) includes an annular slot (42) whereby the slots permit the insertion of an inextensible annular reinforcement element (40) into each of the bead area slots (42) after the molding or casting process. Slots (42) are preferably produced by the addition of annular collars (64) to either the outer member (50) or core member (60) of an improved molding or casting die (48). The improved molding or casting process includes a step of forming a circumferential slot (42) in each tire bead area (16), with these slots (42) permitting the addition of an inextensible annular reinforcement element (40) into each bead area (16) after the molding or casting process.

TECHNICAL FIELD

The field of art to which this invention pertains is that of cast ormolded tires comprised of a body without reinforcing cords, made ofviscoelastic material.

All tires, regardless of their method of manufacture, requirereinforcing elements, commonly referred to as bead wires, embedded inthe bead portions of tires in order to retain each tire on the rim of awheel when the tire is inflated and in use. Thus, these reinforcementelements serve to assure the firm adherence of the tire to the rim.Preferably the annular reinforcement elements are constituted by atleast one shaped metallic element, most often having a circular sectionor by a metal cord of generally circular cross section comprising aplurality of metal wires twisted together. These inextensiblereinforcement elements both retain the tire on the wheel rim and insealing relationship therewith.

In all known tire building processes, the reinforcement elements becomeintegral parts of the tire body. This holds true for bias as well asradial tires and for tires of conventional construction as well as tiresproduced by casting or molding processes.

In known processes, cast or molded tires require the placement of thereinforcement elements inside the mold prior to casting, with thereinforcement elements being held inside the mold by bead clips orlocating blocks in the manner set forth in U.S. Pat. No. 3,381,736 toFord, et al. While filling the mold, the reinforcement elements arefully embedded in and thus become a permanent part of the cast tire.

Therefore, the diameter of the reinforcement elements forms a rigid gateor boundary element through which the mold core has to be removed. Theuse of metal cores is preferred over collapsible or elastic cores sincethe latter do not normally provide the desired degree of accuracy. Theuse of rigid or metal cores requires segmentation and cores with from 8to 16 segments have been previously utilized as evidenced in U.S. Pat.No. 3,922,123 to Spragg, et al., entitled "Core Removal Apparatus" andU.S. Pat. No. 4,083,672 to Vaishnav, entitled "Automatic Hub andApparatus for Disassembly of the Hub," with both of these patents beingassigned to the assignee of the present invention.

Not only is the use of segmented cores very cumbersome, as evidenced bythe above-noted patents, but the manufacture of segmented cores is bothdifficult and expensive. Furthermore, the unavoidable gaps between thecore segments, which leave flash marks on the inner peripheral surfacesof the tires, may adversely affect the performance of the finishedtires. In addition, the sharp corners of the segments tend to cut intothe toe area of the tire when the segments are removed subsequent to thecasting process. A rigid one piece core will not mar the inside of thetire and will not cut the toe area of the tire as it is removedtherefrom. However, until the advent of the present invention, such acore could not be used since the limiting effect of the integralreinforcement elements prohibited the removal of the core after thecasting process. Segmented cores, in addition to being prone tomisalignment and wear, may cause performance deficiencies in thefinished product. The use of segmented cores also makes for a verycumbersome production process since the mold core and outer membersgenerally need to be preheated prior to their use. The requiredinsertion of the reinforcing members into the mold assembly, just priorto casting, make it difficult to automate this process for massproduction.

BACKGROUND ART

U.S. Pat. No. 3,381,736 to Ford, et al., discloses a bead wire locatedby means of blocks mounted on the wire with the blocks being made of amaterial which has similar physical properties to the material of thebead region of the finished tire. Bead wires prepared with such blocksare located, one in each of the bead regions of the tire mold, withpolyurethane thereafter being poured into the mold to form the tire. Ina similar manner, it is also known to manually locate the reinforcingelements in the casting mold by the use of small bead clips.

U.S. Pat. No. 3,924,670 to Tangorra, et al., discloses, in FIG. 6, abead portion of a tire having a circumferential groove therein intowhich reinforcing strands of metallic wire are positioned. However, themetal wires are wound up in a plurality of parallel coils about the tirebead after the positioning of the bead in its own seat of the wheel rim,with the ends of the metal wires being then connected, by means ofconventional known systems, so as to compress the bead against asupporting base of the rim and thereby ensuring the anchorage of the twoparts. Thus, the annular reinforcing element basically functions as aretaining ring which is a separate part and is applied after the tirehas been seated on the rim. Consequently, the tire can be removed fromthe rim only after the retainers or annular elements have been initiallyremoved.

U.S. Pat. No. 4,043,370 to Unwin, et al., discloses a seal arrangementfor an oval tire and rim wherein the base of the tire is formed withannular steps or grooves, inwardly of the tire sidewalls, for receivinga pair of restraining devices or roll restraining hoops. These hoopsseem to accomplish a purpose similar to that of a normal beadreinforcing structure and include elastomeric rings reinforced withwires. This construction appears to be usable only with an oval tire ofa hollow toroidal construction, i.e., a construction without the usualtire bead portions.

DISCLOSURE OF THE INVENTION

The present invention provides a solution to the prior art problemspertaining to the casting or molding of pneumatic tires which hasheretofore required the use of segmented rigid cores. As noted, allknown conventional open-center cast tire constructions and productionprocesses require that the inextensible reinforcement elements, added tothe bead portions of the tires, become integral parts of the tire body.The reinforcement member diameters thus form rigid gates through whichthe rigid segmented core members have to be removed in the manner wellknown in the art and accompanied by the well known production andperformance limitations associated therewith.

The present invention permits the use of a rigid unitary ring-shapedcore member and permits its removal from the tire body after the castingor molding process by adding the required inextensible annularreinforcement elements into each of the tire bead areas after themolding or casting process. By inserting the restrictive inextensiblereinforcement elements into the tire bead areas after the tire has beencast, or cast and cured, the tire sidewalls can be flexed and moved tothe extent that the unitary core member can be removed from the tireinterior. The ease of removal of a non-segmented core member from apost-cast tire will depend greatly on the tire dimension as well as itsaspect ratio. For example, in the case of a bicycle tire, a unitaryrigid metal core can easily be removed by distorting the tire into anoval shape. At the same time, a tire with a high aspect (maximum sectionheight/maximum section width) ratio and a small bead diameter mayrequire the use of heavy duty tools.

In order to permit placement of the reinforcement elements into the casttire bead areas, in a post-cast operation, the tire bead areas must beproduced with a circumferential slot in each of the tire bead areas.

The present invention includes an improved mold or casting die whereinmeans for producing a circumferential slot in each of the bead areas isadded to the die. This may be accomplished by adding a circumferentiallyextending collar to either the outer mold member or the core member,with these collars protruding into the tire bead areas.

The present invention further includes a pneumatic tire produced via amolding or casting process having a cast body, including two sidewallsterminating in first and second bead portions, in combination with firstand second annular inextensible reinforcing elements, with thereinforcing elements being incorporated into the bead portions in apost-cast operation.

The present invention further pertains to a molding or casting processfor the manufacture of pneumatic tires wherein the improvement comprisesthe step of forming a circumferential slot in each of the tire beadareas, with the slots permitting the addition of an inextensible annularreinforcement element into each of the bead areas after the molding orcasting process.

Several preferred non-limiting embodiments are shown by way of examplein the accompanying drawings and described in detail without attemptingto show all the various forms and modifications in which the inventionmight be embodied. After the reinforcement elements have been insertedinto the tire bead slots, the remaining throat or slot openings can beclosed by filling them with liquid urethane, for example, or by closingthe gap with a prefabricated insert or ring member. The features andadvantages of the present invention will become more readily understoodby persons skilled in the art when following the best mode descriptionin conjunction with the several drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents the cross section of a tire, according to the presentinvention, mounted on a wheel rim.

FIG. 2 represents the cross section of a tire body together with oneembodiment of the mold in which it may be manufactured, showing some ofthe parts of the mold separated and in sections.

FIG. 3 represents the cross section of another tire body with a crosssection, partially broken away, of another embodiment of a mold portionused for making said tire body.

FIG. 4 represents a cross section of a further tire body together withyet a further embodiment, in section and partially broken away, of amold portion used for manufacturing the tire body.

FIG. 5 represents a cross section of a portion of a tire body whose beadslot is being closed after the insertion of its reinforcement element.

FIG. 6 represents a cross section of a tire body bead portion whose slotis being closed after the insertion of its reinforcement element.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 represents the cross section of a tire shown generically as 10mounted on any desired type of wheel rim, shown generically as 11. Tire10 consists of a tire body 12 in combination with bead reinforcementelement 40 wherein the former is preferably produced via a molding orcasting process such as for example in a centrifugal tire castingmachine shown and claimed in U.S. Pat. No. 3,924,982 to Yang, et al. Thestructure and operation of this machine can be fully understood bypersons skilled in the art by reference to the disclosure of said patentwhich is incorporated herein by reference to the extent necessary toexplain known practices in this art.

Tire body 12 is comprised of sidewalls 14 terminating on one end in beadportions or areas 16, with the other ends of the sidewalls 14 merginginto shoulder areas 18 which in turn merge into crown portion 22 whichmay include or be provided with an integral or separate tread portion20. Cast tires of this type have previously been disclosed in U.S. Pat.No. Re. 28,424 to McGillvary and U.S. Pat. No. 3,775,528 to Beneze, forexample.

Each tire bead portion 16 terminates in a bead base 26, with the outerintersection of bead base 26 and tire sidewall 14 defining bead heelportion 28 and the inner intersection of bead base 26 and tire sidewall14 defining bead toe portion 30. Looking at it another way, the ends oftire inner peripheral surface 32 and the ends of tire sidewall outersurface 34 merge into the opposite ends of bead base surfaces 36 so asto define the portions of bead toe portion 30 and bead heel portion 28,respectively.

FIG. 1 further shows that tire bead portions 16 are provided withannular or circumferentially extending inextensible reinforcementelements 40, said elements generally comprising at least one shapedmetallic element, of generally circular section. However, the shapes,physical configurations or material compositions of reinforcementelements 40 form no part of and are not limited in terms of the presentinvention.

Annular reinforcement elements 40 are received in tire bead portions 16,preferably being retained by the inner peripheral portion 44 of anannular or circumferentially extending constructed slot, groove orprofiled cavity 42. It is desirable that the cross section of the slotperipheral portion 44 is complementary with the cross section ofreinforcement element 40 selected to preferably provide at least a 180°surface contact therebetween. As shown in FIG. 1, the throat or opening46 of slot 42 may be less than the diameter of reinforcement element 40thereby permitting the press or interference fitting of element 40within slot portion 44. Tire 10 of FIG. 1 has its slots 42 parallel toits axis of rotation 24, with slot throats 46 being open to the interiorof the tire, i.e., slots 42 extending from tire inner surface 32outwardly into tire bead portion 16.

Turning now to FIG. 2, tire body 12, previously described with referenceto FIG. 1, is depicted with one embodiment of a mold or die 48 having anouter mold part or member 50 which has first and second axiallyseparable halves 52 and 54, respectively. Not shown, but readilyunderstood by those skilled in the art, is the fact that mold halves 52and 54 are operatively mounted on support structures for axial andpreferably rotational movement. Outer mold member 50, i.e., mold halves52 and 54, are provided with an inner surface 56 which is constructed soas to form the outer shape or configuration and thus be complementarywith outer surface 34 of tire body 12.

A core part or member 60 is provided for cooperation with outer moldmember 50 and is for the purpose of defining the inner shape of the tirewhich is to be formed in the molding or casting process. Thus, coremember outer surface 62 is complementary with tire inner surface 32. Thespace between core member 60 and outer mold members 52 and 54, when moldor die 48 is in its closed position (not shown), is of course the spacewhich defines the cross section of tire body 12. The formation of slots42 in bead portions 16 are formed by the addition of first and secondannular or circumferentially extending collars 64 laterally extendingfrom core member 60, parallel to tire axis of rotation 24.

Turning now to the FIG. 3 embodiment, there is shown tire body 112 andto the extent that this embodiment is the same as previously describedtire body 12 (FIGS. 1 and 2), reference is made here to the precedingdescription, with like numerals being applicable to like parts.Basically, tire body 112 is substantially similar to tire body 12 exceptthat the former, while also having its slots 42 parallel to its axis ofrotation 24, has its slots 42 extending from tire outer surface 34inwardly into bead portions 16. Furthermore, collars 64, forming slots42, are attached to outer mold half portions 52 and 54 instead of coremember 60 as in the FIG. 2 embodiment.

Turning now to tire body 212 in FIG. 4, this further embodiment is alsosubstantially similar to previously described tire body 12 (FIGS. 1 and2) and reference is made here to this preceding description, with likenumerals being applicable to like parts. This embodiment differs fromtire body 112 of FIG. 3, in that slots 42 are perpendicular rather thanparallel to the axis of rotation 24 of the tire body, i.e., slots 42extend from bead base surface 36 radially outwardly into tire beadportions 16. Collar portions 64, attached to outer mold member halves 52and 54 rather than core member 60 (not shown), are perpendicular to theaxis of rotation 24 of tire body 212.

The several embodiments shown in FIGS. 2, 3 and 4 for forming slots 42are illustrative only and any desired means or process for producingcircumferentially extending or annular slots in tire bead portions 16may be utilized. Collars 64 can be attached or be part of either coremember 60 or outer mold half members 52, 54. If so desired, it is alsopossible to machine slots 42 into the bead areas after production of thetire body.

After the casting or molding of a tire body, and after the mold or diehas been dismounted or disassembled, reinforcement elements 40 can beinserted into slots 42 either by hand or by using an appropriate tool.In addition, reinforcement elements 40 may be inserted into the tirebodies when the latter are in an as-cast or fully vulcanized or curedcondition. Succeeding the insertion of reinforcement elements 40, theremaining throat or slot opening 46 can be closed with a liquid filler68 (such as urethane, for example), in the manner shown in FIG. 5, orvia an insert 70, in the manner shown in FIG. 6.

If slots 42 originate from tire inner surface 32, as shown in FIGS. 1and 2, slot openings 46, remaining after the insertion of reinforcementelements 40, can remain open and need not be filled since there is noforce, after the mounting of the tire on a wheel rim, that tends todislocate reinforcement elements 40 from groove 42 nor can the airescape from the inside of the tire. An added benefit derived when slot42 originates from tire inner surface 32 (FIGS. 1 and 2) is that airpressure in the mounted tire (FIG. 1) also acts on remaining open throatportion 46 thereby tending to press bead toe portion 30 against wheelrim 11 and thus assisting in the fluid-tight sealing of the tire to therim.

From the foregoing description, and the operational discussion, it isbelieved that those familiar with the art will readily recognize andappreciate the novel concepts and features of the present invention.Obviously, while the invention has been described in relation to only alimited number of embodiments, numerous variations, changes,substitutions and equivalents will present themselves to persons skilledin the art and may be made without necessarily departing from the scopeand principles of this invention. As a result, the embodiments describedherein are subject to various modifications, changes and the likewithout departing from the spirit and scope of the invention with thelatter being determined solely by reference to the claims appendedhereto.

What is claimed is:
 1. In a pneumatic tire comprising a molded or castseamless toroidal body extending continuously from one annular beadportion to the other, encompassing sidewalls and at least a crown arearadially inward of an annular road-engaging tread, said sidewallsconnecting the lateral edges of said tread to said bead portions, eachbead portion containing an independent unitary annular substantiallyinextensible reinforcing element, the improvement comprising theaddition of means for producing an integral circumferential constrictedslot in each of said bead areas during said molding or casting processto permit an interference-fitting of said reinforcing elementssubsequent to said molding or casting process, with the cross section ofeach constricted slot being complementary with the cross section of eachreinforcing element to the degree of providing an at least 180° surfacecontact therebetween.
 2. The improved tire of claim 1 wherein said meansfor producing said constricted slots includes first and second annularprofiled collars added to the mold or casting die, wherein said collarsprotrude into said first and second bead areas respectively.
 3. Theimproved tire of claim 2 wherein said mold or casting die includes outermembers and a core member, wherein said profiled collars are added toone of said outer member and said core member.
 4. The improved tire ofclaim 3 wherein said profiled collars are added to said outer members.5. The improved tire of claim 3 wherein said profiled collars are addedto said core member.
 6. The improved tire of claim 1 wherein saidconstricted slots are parallel to the axis of rotation of said tire. 7.The improved tire of claim 6 wherein said constricted slots extend fromthe outer surface of said tire laterally inwardly into said bead areas.8. The improved tire of claim 6 wherein said constricted slots extendfrom the inner surface of said tire laterally outwardly into said beadareas.
 9. The improved tire of claim 1 wherein said constricted slotsare perpendicular to the axis of rotation of said tire.
 10. The improvedtire of claim 9 wherein each constricted slot extends from the basesurface of each bead portion of said tire radially into said beadportion.
 11. The improved tire of claim 1 wherein each constricted slotincludes an opening having a cross section less than that of the crosssection of said reinforcing element.
 12. The improved tire of claim 11including means for closing said opening after insertion of saidreinforcing element.
 13. The improved tire of claim 1 wherein said tirebody is molded or cast of polyurethane polymer.
 14. The improved tire ofclaim 1 wherein said degree of surface contact between said slot andreinforcing element is about 270°.
 15. The improved tire of claim 1wherein said constricted slot takes the form of a profiled open cavity.